1. Field
The present invention relates generally to wireless communication devices, and more specifically to determining the location of wireless communication devices.
2. Background
The explosive growth of wireless communications has resulted in many new and valuable services being available to individuals. Many of the new services use information about the individual's location to deliver services that are personalized to an individual based on the individual's location. These types of services are sometimes referred to as Location Based Services (LBS).
Wireless communication devices have become ubiquitous in modem society. For example, many, if not most, individuals today own a cell phone. One advantage of these wireless devices, such as cell phones, is that they allow individuals to communicate while the individual is mobile. Mobility increases the challenges of providing LBS because there is no way to know ahead of time where a particular individual, or wireless device, will be located.
Many different types of LBS have been developed. For example, an individual can be provided driving directions, or could be shown ads specific to the region where the user is traveling, or some other type of information that would be valuable to an individual based on their location. Another location based service that is of great importance is locating a wireless caller that has dialed an emergency operator, or 911 operator. In the United States, calling 9-1-1 will immediately connect the caller to an emergency service operator. For example, in the United States, the Federal Communication Commission established a four-year rollout schedule, that began in Oct. 1, 2001, requiring wireless carriers to develop technologies that can provide the location of wireless callers to 9-1-1. This mandate is referred to as enhanced 911, or E911. Location service could also be used to improve aspects of a wireless communication system. For example, location service can be used to facilitate handoff in a communication system as described in U.S. Pat. No. 6,321,090 entitled“MOBILE COMMUNICATION SYSTEM WITH POSITION DETECTION TO FACILITATE HARD HANDOFF” by Soliman, filed Nov. 6, 1998, assigned to the assignee of the present application and incorporated herein in its entirety.
Two main technologies are currently used to locate a wireless device. One technique, referred to as a “network” solution, determines location of the wireless device from information obtained in the wireless network infrastructure based on interaction between a wireless device and the infrastructure. For example, the location of a receiver in the infrastructure, for example, a cell tower, that receives a wireless call is known, thereby locating a wireless device placing the call to be within the coverage area of the receiving cell tower. Also, if the transmission from a wireless device is received at several cell towers, then a form of triangulation, based on overlap of multiple cell coverage areas, may be used to determine a location of the wireless device placing the call. The wireless device can also determine its location if it receives signals from multiple, different, cell towers. In general, these techniques are not very accurate and do not work well where the infrastructure is not dense, such as in rural areas where a single cell tower may service a large region.
Another technology, referred to as a “handset” solution, uses information obtained in the wireless device, or handset, to determine the location of the wireless device. Many handset solutions use signals received at the wireless device that have been transmitted from satellites within the Global Positioning System (GPS) constellation to determine the location of the wireless device. Location based on GPS is generally much more accurate than network based solutions, but GPS signals are fairly weak, and may be “blocked” by foliage, structures, or other items in the path of the GPS signals. For example, it is generally difficult to receive GPS signals when the receiver (handset) is located within a building.
Other “hybrid” solutions have been developed to take advantage of the benefits of both a network based and a handset solution. While these hybrid techniques provide a significant advantage over either the network or handset solutions alone, there are still instances where improved accuracy is desirable.
There is therefore a need in the art for improving the determination of the location of wireless devices.